Sigma 210101 18-35mm F1.8 DC HSM Lens for Canon APS-C DSLRs
This is an APS-C (EF-S mount) zoom lens with a constant f/1.8 aperture, making it the fastest zoom available for Canon cameras. It looks like a typo, doesn't it? Well, it not and this sure isn't your daddy’s Sigma. As a member of Sigma's Art line-up, this lens performs as we've come to expect from Art lenses. Throughout its admittedly short range the images this lens produces are pristine, with sharpness across the frame from end to end. But hold your breath, that's still not its greatest feature.
In a first for the industry, this lens has a constant maximum aperture of a whopping f/1.8, making it extremely fast at all focal lengths. APS-C sensors are smaller than the conventional 35mm "full-frame" sensors, but they often have higher pixel densities. More importantly, smaller sensors have larger depth-of-focus than their full-frame counterparts at a given aperture and focal length. This lens has a rather dramatically large aperture which counters this thinner depth-of-focus phenomenon somewhat.
The science of why that is isn't important for this review, just know that the professional effect of a razor sharp subject sitting in a thin depth-of-focus set in a smooth, blurry background is better achieved on a camera with a small sensor by using lenses with extremely large maximum apertures. The Sigma 18-35mm f/1.8 DC HSM Art is such a lens, and it's a ZOOM!
Since this lens is designed for Canon's crop sensors you need to convert the focal length of the lens to get a better idea of the field-of-view the lens offers. For instance, at 35mm this lens will give you an equivalent field-of-view of a 56mm lens on a full-frame camera. So you should consider this a
wide-angle to standard length zoom since it offers no telephoto focal lengths. That might be a concern for some looking for a more complete walk-around lens with the option to go longer without having to swap lenses.
Made with four aspherical elements and five special low dispersion glass elements, the Sigma 18-35mm f/1.8 DC HSM Art packs quite a punch where glass technology is concerned. This lens is also user-adjustable with Sigma's USB calibration dock to assure this lens will be sharp (and stay sharp) for many years of use. Compared to other professional quality zoom lenses, this lens is priced very competitively.
If you’re looking for a walk-around lens that allows you razor-thin depth-of-focus on your Rebel, 60D, 70D, or any Canon crop camera, you would be wise to consider theSigma 18-35mm f/1.8 DC HSM Art zoom lens.